1. Field
Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to wireless signal interference management.
2. Background
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.
In some wireless networks, such as UMTS networks, user equipment (UE) may operate in several states, two of which are CELL_DCH and CELL_FACH. The CELL_DCH state is characterized by having a dedicated physical channel in the uplink and downlink and the ability to engage in soft handover procedures. UEs in the CELL_FACH state, however, do not have a dedicated physical channel and are unable to engage in soft handover. This lack of ability to engage in soft handover in the CELL_FACH state can potentially lead to uplink interference at a neighbor cell, especially in instances where a high number of UEs in CELL_FACH camp on a serving cell adjacent to the neighbor cell.
Furthermore, cell reselection procedures in CELL_FACH are slow and cumbersome. As a result, when a UE operating in CELL_FACH initiates a transmission on the uplink, the serving cell may not be the strongest cell on the downlink. In the absence of any uplink imbalance between the serving cell and the neighboring strongest downlink cell, the UE uplink transmission may cause interference at the neighbor cell or cells. Additionally, even if the serving cell is the strongest downlink cell, if an uplink to a neighbor cell were stronger than the uplink to the serving cell, an uncontrollable interference condition could exist at the neighbor cell.
This interference phenomenon may also occur in heterogeneous networks, which may include network access devices of various forms, technologies, and network types, such as picocells, femtocells, cellular base stations, macrocells, small cells and the like. In heterogeneous networks, soft handoff may not be available due to the varying technologies of the network access devices and/or cells, so uplink interference may occur where a UE is in CELL_FACH mode on a serving cell near another network access device.